Luminescent apparatus and method of manufacturing the same

ABSTRACT

The present invention provides a luminescent apparatus having a bright, high-quality image. A reflecting surface-including electrode, and an EL element formed of an organic EL layer and a transparent electrode are provided on an insulator. As shown in FIG.  1 , an auxiliary electrode  107  formed of a transparent conductive film is connected to the transparent electrode via a conductor. This structure enables a resistance value of the transparent electrode  104  to be substantially lowered, and a uniform, voltage to be applied to the organic EL layer.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a luminescent apparatus using a thinfilm made of a luminescent material, and also to an electric applianceusing the luminescent apparatus as a display. An organic EL display andan organic light-emitting diode (OLED) are included in the luminescentapparatus according to the present invention.

[0003] The luminescent materials which can be used for the presentinvention include all luminescent materials that emit light(phospholescence and/or fluorescence) via singlet excitation or tripletexcitation or both thereof.

[0004] 2. Description of the Related Art

[0005] In recent years, the development of a luminescent element(hereinafter referred to as EL element) using a thin film (hereinafterreferred to as EL film) made of a luminescent material capable ofobtaining EL (electroluminescence) has been forwarded. A luminescentapparatus (hereinafter referred to as EL luminescent apparatus) has anEL element having a structure in which an EL film is held between ananode and a cathode. This apparatus is adapted to obtain luminescence byapplying a voltage between the positive and cathode. Especially, anorganic film used as an EL film is called an organic EL film.

[0006] A metal (typically, a metal of Group I or II on the, periodictable) having a small work function is used as a cathode in many cases,while a conductive film (hereinafter referred to as a transparentconductive film) transparent with respect to visible light is used as ananode in many cases. Owing to such a structure, the luminescenceobtained passes through the anode, and is visually recognized.

[0007] Recently, the development of an active matrix type EL luminescentapparatus adapted to control the luminescence of an EL element providedin each image element by using a TFT (thin film transistor) has beenforwarded, and a prototype thereof has come to be made public. Theconstructions of active matrix type EL luminescent apparatuses are shownin FIGS. 9A and 9B.

[0008] Referring to FIG. 9A, a TFT 902 is formed on a substrate 901, andan anode 903 is connected to the TFT 902. An organic EL film 904 and acathode 905 are formed on the anode 903, and an EL element 906 includingthe anode 903, organic EL film 904 and cathode 905 is thereby formed.

[0009] In this luminescent apparatus, the luminescence generated in theorganic EL film 904 passes through the anode 903, and is emitted in thedirection of an arrow in the drawing. Therefore, the TFT 902 becomes aluminescence screening object from an observer's viewpoint, and causesan effective emission region (region in which an observer can makeobservation of luminescence) to be narrowed. In order to obtain a brightimage when the effective emission region is narrow, it is necessary toincrease an emission brightness but increasing the emission brightnessresults in an early deterioration of the organic EL film.

[0010] Under these circumstances, an active matrix type EL luminescentapparatus of a structure shown in FIG. 9B has been proposed. Referringto FIG. 9B, a TFT 902 is formed on a substrate 901, and a cathode 907 isconnected to the TFT 902. An organic EL film 908 and an anode 909 areformed on the cathode 907, and an EL element 910 including the cathode907, organic EL film 908 and the anode 909 are thereby formed. That is,this EL element 910 constitutes a structure directed contrariwise withrespect to the EL element 906 shown in FIG. 9A.

[0011] In the luminescent apparatus of FIG. 9B, the luminescencegenerated theoretically in the EL film 908 passes through the anode 909,and is emitted in the direction of an arrow in the drawing. Accordingly,the TFT 901 enables the whole region, which is provided in a positionwhich cannot be seen by an observer, and which has the electrode 907thereon, to be used as an effective emission region.

[0012] However, the structure shown in FIG. 9B has potentially a problemthat the structure is incapable of applying a uniform voltage to theanode 909. It is known that a resistance value of a transparentconductive film used generally as an anode is high as compared with thatof a metallic film and can be reduced by thermally treating thetransparent film. However, since the organic EL film has a low thermalresistance, a thermal treatment of over 150° C. cannot be conductedafter the organic EL film has been formed.

[0013] Therefore, when an anode (transparent conductive film) islaminated on an organic EL film, a thermal treatment cannot beconducted, so that it is difficult to form an anode of a low resistancevalue. That is, there is a possibility that a level of a voltage appliedto the anode differs at an end portion and a central portion thereof.There is a fear that this problem causes a decrease in the quality of animage.

[0014] As mentioned above, in a luminescent apparatus including astructure using a transparent conductive film formed after the formationof an organic EL film, it is difficult to reduce the resistance of thetransparent conductive film.

SUMMARY OF THE INVENTION

[0015] The present invention has been made in view of the abovecircumstances, and it is an object of the invention to provide aluminescent apparatus capable of displaying a bright, high-qualityimage, and also an electric appliance using such a luminescent apparatusas a display and capable of displaying an image of a high quality. Thepresent invention will be described with reference to FIG. 1.

[0016] According to an aspect of the present invention, the method ofmanufacturing a luminescent apparatus has the step of connecting anauxiliary electrode to a transparent electrode, which is provided afterthe formation of an organic EL film, in parallel therewith so as tosubstantially reduce the resistance of the transparent electrode.

[0017] Referring to FIG. 1, a reference numeral 101 denotes aninsulator, 102 an electrode including a reflecting surface, 103 anorganic EL layer, and 104 an electrode (hereinafter referred to astransparent electrode) transparent or translucent with respect to thevisible light. On the insulator 101, an EL element formed of theelectrode 102 including a reflecting surface, organic EL layer 103, andtransparent electrode 104 is formed.

[0018] The phrase “transparent with respect to the visible light” meansthat the visible light is transmitted with a transmission factor of80-100%. The phrase “translucent with respect to the visible light”means that the visible light is transmitted with a transmission factorof 50-80%. Although the transmission factor differs depending upon thethickness of a film, of course, the thickness of a film may be designedsuitably so that the transmission factors be within the above-describedrange.

[0019] The insulator 101 may be formed of an insulating substrate or asubstrate provided with an insulating film on a surface thereof as longas it can support the EL element.

[0020] The electrode 102 including a reflecting surface means a metallicelectrode or an electrode formed of a lamination of a metallic electrodeand a transparent electrode. That is, the electrode 102 means anelectrode including a surface (reflecting surface) capable of reflectingthe visible light on an outer surface or a rear surface thereof or aninterface in the interior thereof.

[0021] The organic EL layer 103 used can be formed of an organic EL filmor a laminated film of an organic EL film and a film of an organicmaterial. That is, an organic EL film may be provided singly as aluminescent layer, or a layer of an organic material as acharge-injected layer or a charge carrying layer may be laminated on anorganic EL layer as a luminescent layer. The inorganic materials includea material capable of being used as a charge-injected, layer or a chargecarrying layer, and a layer of such an inorganic material can also beused as a charge-injected layer or a charge carrying layer.

[0022] The transparent electrode 104 can be formed of an electrode of atransparent conductive film or an electrode of a metallic film(hereinafter referred to as a translucent metallic film) of 5-70 nm(typically, 10-50 nm) in thickness. The transparent conductive film canbe formed of a conductive oxide film (typically, an indium oxide film, atin oxide film, a zinc oxide film, a compound film of indium oxide andtin oxide, a compound film of indium oxide and zinc oxide), or amaterial obtained by adding gallium oxide to a conductive oxide film.When a transparent conductive film is used as the transparent electrode104, its thickness is set to 10-200 nm (preferably 50-100 nm), and thisenables the electrode to transmit the visible light with a transmissionfactor of 80-95%.

[0023] On the EL element 105 formed of the above-described structure, aseal member 106 and an auxiliary electrode 107 are provided, and theauxiliary electrode 107 is electrically connected to the transparentelectrode 104 via anisotropic conductors 108. The anisotropic conductors108 scattering on the transparent electrode 104 are preferably providedso that they are distributed over the whole surface thereof.

[0024] The seal member 106 is a substrate or a film transparent withrespect to the visible light, and a glass substrate, a quartz substrate,a crystallized glass substrate, a plastic substrate, or a plastic filmcan be used. When a plastic substrate or a plastic film is used, it ispreferable to provide an outer surface of a rear surface thereof with aprotective film (preferably a carbon film, specifically a diamond-likecarbon film) capable of preventing the passage of oxygen and watertherethrough.

[0025] The auxiliary electrode 107 is an electrode provided auxiliarilyfor the purpose of reducing a resistance value of the transparentelectrode 104, and can be made of an electrode formed of a transparentconductive film or an electrode formed of a translucent metallic filmjust as the transparent electrode 104. When the thickness of theauxiliary electrode 107 is set to 10-200 nm (preferably 50-100 nm) inthe same manner as that of the transparent electrode 104, the auxiliaryelectrode can transmit the visible light with a transmission factor of80-95%.

[0026] The anisotropic conductors 108 can be formed by using anisotropicconductive films. The anisotropic conductive film is a resin film inwhich conductive particles (typically metallic particles or carbonparticles) are dispersed uniformly. According to the present invention,it is preferable that the anisotropic conductive films 108 be providedselectively by patterning them by photolithography, by an ink jetmethod, or a printing method. The reason resides in the low transmissionfactor of the anisotropic conductive film with respect to the visiblelight. Therefore, when the anisotropic conductors are provided over thewhole surface of the transparent electrode 104, the light emitted fromthe organic EL layer 103 is absorbed thereinto.

[0027] In the luminescent apparatus including the above-describedstructures according to the present invention, the auxiliary electrode107 functions as an electrode connected to the transparent electrode104, which is formed of a transparent conductive film, in paralleltherewith. Since the auxiliary electrode 107 is formed on the side ofthe seal member 106, a resistance value can be reduced to a low levelwithout being restricted by the low thermal resistance of the organic ELfilm referred to in the descriptions of the related art examples.Therefore, when the present invention is put into practice, it becomespossible to apply a uniform voltage to the transparent electrode 104 andobtain an image of a high quality.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Preferred embodiments of the present invention will be describedin detail on the basis of the following figures, wherein:

[0029]FIG. 1 is a drawing showing in section the construction of aluminescent apparatus;

[0030]FIG. 2 is a drawing showing in section the construction of aluminescent apparatus;

[0031]FIG. 3 is a drawing showing the steps of manufacturing aluminescent apparatus;

[0032]FIG. 4 is a drawing showing the steps of manufacturing aluminescent apparatus;

[0033]FIG. 5 is a drawing showing the construction of an upper surfaceof a pixel of a luminescent apparatus and the construction of a circuitthereof;

[0034]FIG. 6 is a drawing showing in section the construction of aretention capacitor;

[0035]FIG. 7 is a drawing showing in section the construction of aluminescent apparatus;

[0036]FIG. 8 is a drawing showing the construction of an upper surfaceof the luminescent apparatus; and

[0037]FIG. 9 is a drawing showing in section the construction of relatedart luminescent apparatuses.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] A mode of embodiment of the present invention will now bedescribed with reference to FIG. 2. Referring to FIG. 2, a referencenumeral 201 denotes a substrate on which elements are formed. Accordingto the present invention, any material may be used for the substrate201. That is, glass (including quartz glass), crystallized glass,monocrystalline silicon, a ceramic material, a metal, or a plastic canbe used.

[0039] A pixel 202 is formed on the substrate 201, and has a structureincluding a switching TFT 203 and a current control TFT 204. FIG. 2shows three pixels emitting red, green, or blue light respectively. Theswitching TFT 203 functions as a switch to input video signals into thepixels, and the current control TFT 204 functions as a switch forcontrolling a current flowing in an EL element. In this embodiment, adrain of the switching TFT 204 is electrically connected to a gate ofthe current control TFT 204.

[0040] Limitations are not placed on the construction of the switchingTFT 203 and current control TFT 204. A top gate type (typically, aplanar type) TFT or a bottom gate type (typically, an inverselystaggered type) TFT may be used. An n-channel type TFT or a p-channeltype TFT may be used for both of these TFTs.

[0041] The switching TFT 203 and current control TFT 204 are coveredwith an inter-layer insulating film 205, to an upper portion of which apixel electrode 207 formed of a metallic film and a drain of the currentcontrol TFT 204 are electrically connected via anisotropic conductiveplugs 206. On the pixel electrode 207, a first transparent electrode 20810-200 nm (preferably 50-100 nm) thick is laminated. In this embodiment,the pixel electrode 207 and first transparent electrode 208 form ananode 230.

[0042] This mode of embodiment employs a structure in which contactholes in which the drain of the current control TFT 204 and pixelelectrode 207 are connected together are filled with anisotropicconductors. These anisotropic conductors provided so as to fill thecontact holes therewith are called anisotropic conductive plugs. Theanisotropic conductive plugs 206 may be formed by etching an anisotropicconductive film. Of course, the pixel electrode 207 may be connecteddirectly to the drain of the current control TFT 204.

[0043] In recesses due to these contact holes, the coverage of theorganic EL layers is poor, and there is a fear of causingshort-circuiting of the cathode and the anode, so that such recesses arenot desirable. In this mode of embodiment, the formation of the recessesdue to the contact holes of the pixel electrode 207 can be prevented byusing the anisotropic conductive plugs 206, and this enables theprevention of the occurrence of the short-circuiting of the cathode andthe anode.

[0044] The pixel electrode 207 is formed preferably by using a metallicfilm of a high reflectance, such as an aluminum, film (including analuminum alloy film and an additive-containing aluminum film), or a thinsilver film. A film formed by coating a metallic film with aluminum orsilver may also be used.

[0045] A reference numeral 209 denotes insulating films (hereinafterreferred to as banks) provided between portions of the anode 230, andformed so as to cover level-different portions at end sections of theanode 230. In this mode of embodiment, the provision of the banks 209keeps the organic EL layers away from end sections of the anode 230which are liable to give rise to field concentration, and thedeterioration, which is ascribed to the field concentration, of theorganic EL layers is thereby prevented. The banks 209 may be formed byusing either resin films or silicon-containing insulating films(typically, a silicon oxide films).

[0046] A reference numeral 210 denotes an organic EL layer emitting redlight, 211 an organic EL layer emitting green light, and 212 an organicEL layer emitting blue light. The construction of the organic EL layers210-212 may be selectively determined with reference to knowntechniques.

[0047] A second transparent electrode 213 provided so as to cover theorganic EL layers 210-212 is an electrode for injecting electrons intothe organic EL layers. A work function of this second transparentelectrode 213 is preferably 2.5-3.5 eV, and this electrode may be formedby using a metallic film containing an element belonging to Group I orII on the periodic table. In this embodiment, an alloy film (hereinafterreferred to as Al—Li film) formed by coevaporating aluminum and lithium.Since the Al—Li film is a metallic film, it can be used as a transparentelectrode by setting its thickness to 10-70 nm (typically, 20-50 nm).

[0048] On this second transparent electrode a third transparentelectrode 214 formed of a 100-300 nm (preferably 150-200 nm) thicktransparent conductive, film is provided. The third transparentelectrode 214 is an electrode adapted to fulfill the function ofapplying a voltage to the second transparent electrode 213. In thisembodiment, the second and third transparent electrodes 213, 214 formtogether a cathode 231.

[0049] A seal member 215 provided so as to be opposed to the substrate201 (which is called in this embodiment a substrate including a thinfilm provided on the substrate 201) has an auxiliary electrode (fourthtransparent electrode) 216 formed thereon which is made of a transparentconductive film 10-200 nm (preferably 50-100 nm) thick. The thirdtransparent electrode 214 and the auxiliary electrode 216 areelectrically connected together via anisotropic conductors 217 each ofwhich is formed of an anisotropic conductive film (resin film in whichmetallic particles or carbon particles are dispersed).

[0050] It is preferable that the anisotropic conductors 217 be providedpartially on the third transparent electrode 214. That is, it isdesirable that the anisotropic conductive film be provided so as not tobe superposed on at least an emission region of the pixels since thisfilm is black or gray. When the anisotropic conductive film is usedpositively as a black matrix by providing the same among pixels, theoptical directivity of each pixel can, of course, be improved.

[0051] The substrate 201 and seal member 215 are pasted on each other bya sealant (not shown) provided on outer edge portions of the substrate201. When the substrate 201 and the seal member 215 are pasted on eachother, a spacer (preferably 1-3 μm thick) for defining a clearancebetween the substrate 201 and the seal member 215 may be provided.Especially, providing the anisotropic conductors 217 so that they servealso as spacers is effective.

[0052] It is preferable that a nitrogen gas or a rare gas be sealed in aspace 218 formed between the substrate 201 and the seal member 215. Itis desirable to provide this space 218 with a material having ahygroscopicity or a material having deoxidization characteristics.

[0053] The detailed construction of a region 219 is shown in FIG. 2B.Referring to FIG. 2B, an anode 230, an organic EL layer 212, and acathode 231 form an EL element 220. The most characteristic point of theluminescent apparatus shown in FIG. 2A resides in that the emission oflight is observed through the cathode 231.

[0054] Out of the light generated in the EL element 220, the lightadvancing toward the anode 230 is reflected on the pixel electrode 207having a surface of a high reflectance, and the resultant light advancestoward the cathode 231. That is, the pixel electrode 207 is an electrodeadapted to supply (extract electrons) a current to the anode 230, andalso having a function of a reflector.

[0055] Since the second transparent electrode 213 has an extremely smallthickness, a resistance value thereof is high. Therefore a thirdtransparent electrode 214 is laminated on the electrode 213 so as tolower the resistance value of the latter. However, since the transparentconductive film used for the third transparent electrode 214 is formedafter the organic EL layer has been formed, it is difficult to lower theresistance value of the second transparent electrode. Therefore, in thismode of embodiment, the auxiliary electrode 216 made of a transparentconductive film is connected to the third transparent electrode 214,which is made of a transparent conductive film, in parallel therewith soas to substantially reduce the resistance of the third transparentelectrode 214.

[0056] In the luminescent apparatus of the above-described construction,a pixel as a whole forms an effective emission region, so that a verybright image can be obtained.

[0057] When the present invention is put into practice, a uniformvoltage can be applied to the cathode as a whole, and this enables animage of a high quality to be obtained.

Embodiments Embodiment 1

[0058] In this embodiment, the steps of manufacturing the luminescentapparatus shown in FIG. 2 will be described with reference to FIGS. 3-5.FIGS. 3 and 4 are sectional views showing the steps for manufacturing apixel portion. A top view (of the condition at a point in time at whichan anode has been just formed) of a pixel formed according to thisembodiment is shown in FIG. 5A, and a circuit diagram of a final pixelin FIG. 5B. The reference numerals used in FIG. 5 correspond to thoseused in FIGS. 3 and 4.

[0059] First, as shown in FIG. 3A, a glass substrate 301 is prepared asa substrate, and a base film 302 made of a silicon oxide film is formedthereon to a thickness of 200 nm. The forming of the base film 302 maybe done by using a low pressure thermal CVD method, a plasma CVD method,a sputtering method, or a vapor deposition method.

[0060] A crystalline silicon film 303 is then formed to a thickness of50 nm on the base film 302. A known method can be used as a method offorming the crystalline silicon film 303. An amorphous silicon film maybe laser crystallized by using a solid state laser or an excimer laser,or crystallized by a thermal treatment (furnace annealing). In thisembodiment, an amorphous silicon film is crystallized by irradiationwith an excimer laser beam using a XeCl gas.

[0061] Next, as shown in FIG. 3B, the crystalline silicon film 303 ispatterned to form island-like crystalline films 304, 305. A gateinsulating film 306 made of a silicon oxide film is formed to athickness of 80 nm so as to cover the island-like crystalline siliconfilms 304, 305. Gate electrodes 307, 308 are further formed on the gateinsulating film 306. According to the drawing, the gate electrode 307 isapparently formed of two separate parts but it is actually the same,bifurcated electrode.

[0062] In this embodiment, a tungsten film or a tungsten alloy film 350nm thick is used as a material for the gate electrodes 307, 308. Otherknown materials can also be used, of course, as the materials for thegate electrodes. In this embodiment, a connecting wire 309 is alsoformed simultaneously with these gate electrodes. The connecting wire309 is a wire for electrically connecting a source of a current controlTFT and a current supply wire together later.

[0063] Next, as shown in FIG. 3C, an element (typically, boron)belonging to the 13th group of the periodic table is added by using thegate electrodes 307, 308 as masks. The adding of the element may be doneby a known method. Thus, impurity regions (hereinafter referred to asp-type impurity regions) 310-314 indicative of p-type conductive typeregions are formed. Just under the gate electrodes, channel-formingregions 315 a, 315 b, 316 are defined. The p-type impurity regions310-314 constitute source regions or drain regions of the TFT.

[0064] The activation Of the element belonging to the 13th group of theperiodic table and added by conducting a thermal treatment is thencarried out. The pattern formed of the island-like crystalline siliconfilm subjected to various steps up to this activation step is called anactivated layer. This activation step may be carried out by furnaceannealing, laser annealing, lamp annealing, or a combination thereof. Inthis embodiment, a thermal treatment is carried out at 500° C. for 4hours in a nitrogen atmosphere.

[0065] In this activation step, it is desirable that oxygenconcentration in the treatment atmosphere be set not higher than 1 ppm(preferably not higher than 0.1 ppm). The reasons reside in that, whenthe oxygen concentration is high, the surfaces of the gate electrodes307, 308 and the connecting wire 309 are oxidized to cause it difficultto bring these parts into electrical contact with a gate wire and acurrent supply wire which are to be formed later.

[0066] It is effective that a hydrogenation treatment be carried outafter the end of the activation step. The hydrogenation treatment may beconducted by using known hydrogen annealing techniques or plasmahydrogenation techniques.

[0067] As shown in FIG. 3D, a current supply line 317 is formed so thatthis supply line contacts the connecting wire 309. When such a structure(a top view of which is shown in a region designated by 501 in FIG. 5A)is formed, the connecting wire 309 and the current supply wire 317 areelectrically connected together. During this time, a gate wire (shown ina region designated by 502 in FIG. 5A) is also formed at the same time,and electrically connected to the gate electrode 307. A top view of thisstructure is shown in a region designated by 503 in FIG. 5A.

[0068] In the region designated by 503, the gate wire 502 has aprojecting portion, i.e., the gate wire 502 is redundantly designed soas to secure a portion which does not get over the gate electrode 307.The reason why, the gate wire 502 is formed in this manner resides inthat, even when the gate wire 502 is broken in the portion in which thegate wire 502 gets over the electrode 307, the electrical breakage ofthe gate wire 502 in the mentioned portion can be avoided. The purposeof forming the gate electrode 307 to the shape of the letter “C” is alsoto redundantly design the same so that a voltage is applied reliably toboth electrodes.

[0069] This current supply wire 317 and the gate wire 502 are formed ofa metallic film the resistance of which is lower than those of theconnecting wire 309 and gate electrode 307. Preferably, a metallic filmcontaining copper or silver may be used. That is, a metallic film of ahigh processability is used for a gate electrode demanding a highpatterning accuracy, and a metallic film of a low specific resistancefor pass lines (gate wire and current supply wire in this embodiment)demanding a low specific resistance.

[0070] After the gate wire 502 and the connecting wire 309 have beenformed, a first interlayer insulating film made of a silicon oxide filmis formed to a thickness of 800 nm. The forming of this film may be doneby using a plasma CVD method. Some other inorganic insulating film or aresin (organic insulating film) may be used as or for the firstinterlayer film 318.

[0071] Next, as shown in FIG. 3E, wires 319˜322 are formed by makingcontact holes in the first interlayer film 318. In this embodiment,metallic wires each of which is formed of a three-layer structure oftitanium, aluminum, and titanium are used as the wires 319-322. Anymaterials may, of course, be used as long as they are in the form ofconductive films. The wires 319-322 are used as source wires or drainwires of TFT.

[0072] The drain wire 322 of the current control TFT is electricallyconnected to the connecting wire 309. As a result, the drain of acurrent control TFT 402 and the current supply wire 317 are electricallyconnected together.

[0073] A switching TFT 401 and current control TFT 402 are completed inthis condition. Although both of these TFTs are formed of a p-channeltype TFT in this embodiment, both or either one of them may be formed ofan n-channel type TFT.

[0074] The switching TFT 401 is formed so that the gate electrodecrosses the active layer at two portions thereof, and has a structure inwhich two channel-forming regions are connected in series. When the TFT401 is formed to such a structure, an off-current value (value of acurrent flowing when the TFT is turned off) can be reduced effectively.

[0075] In the pixel, a holding capacitor 504 is formed as shown in FIG.5A. A sectional view (taken along a line B-B′ in FIG. 5A) of the holdingcapacitor 504 is shown in FIG. 6. The holding capacitor 504 is formed ofa semiconductor layer 505 electrically connected to the drain of thecurrent control TFT 402, the gate insulating film 306 and a capacitorwire 506. That is, the semiconductor layer 505 and a capacitor wire 506are insulated by the insulating film 306, and form a capacitor (holdingcapacitor).

[0076] The capacitor wire 506 is formed simultaneously With the gatewire 502 and current supply wire 317, and serves also as a wire forelectrically connecting the gate electrode 308 and connecting wire 507together. The connecting wire 507 is electrically connected to the drainwire (which functions as a source wire in some cases) 320 of theswitching TFT 401.

[0077] The advantage of the holding capacitor shown in this embodimentresides in that the capacitor wire 506 is formed after the active layerhas been formed. That is, since the semiconductor layer 505 constitutesa p-type impurity region in the case of this embodiment, it can be usedas it is as an electrode.

[0078] After the wires 319-322 are formed, a passivation film 323 madeof a silicon nitrogen film or a nitrided silicon oxide film is formed toa thickness of 200 nm. When a hydrogenation treatment is conductedbefore or after this passivation film 323 is formed, the electriccharacteristics of the TFT can be improved.

[0079] As shown in FIG. 4A, a layer of an acrylic resin is then formedto a thickness of 1 μm as a second interlayer insulating film 324. Aftera contact hole 325 is made, an anisotropic conductive film 326 isformed. In this embodiment, a layer of an acrylic resin in which silverparticles are dispersed is used as the anisotropic conductive film 326.It is desirable that the anisotropic conductive film 326 be formed tosuch a sufficient thickness that permits flattening the contact hole325. In this embodiment, the anisotropic conductive film 326 is formedto a thickness of 1.5 μm by a spin coating method.

[0080] The anisotropic conductive film 326 is then etched with plasmausing an oxygen film. This process is continued until the secondinterlayer insulating film 324 is exposed. When the etching of the film326 finishes, an anisotropic conductor plug 327 shown in FIG. 4B comesto be formed. When the second interlayer insulating film 324 is exposed,a height difference occurs in some cases in the anisotropic conductorplug 327 with respect to the second interlayer insulating film 324, dueto a difference in etching rate therebetween but, when the heightdifference is not larger than 100 nm (preferably not larger than 50 nm),it does not raise any special problem.

[0081] After the anisotropic conductor plug 327 is formed, an aluminumfilm to which scandium or titanium is added and an ITO film (compoundfilm of indium oxide and tin oxide) are accumulated thereon. Theresultant product is subjected to etching to form a pixel electrode 328made of an aluminum film to which scandium or titanium is added and afirst transparent electrode 329 made of an ITO film. In this embodiment,the pixel electrode 328 and the first transparent electrode 329constitute an anode 340.

[0082] In this embodiment, the thickness of the aluminum film is set to200 nm, and that of the ITO film 100 nm. The ITO film can be etched withITO-04N (commercial name of the etching solution for ITO films,manufactured by the Kanto Kagaku Co., Ltd.), and the aluminum film by adry etching method using a gas obtained by mixing carbon tetrachloride(SiCl₄) and chlorine (Cl₂).

[0083] A sectional view of FIG. 4B of the structure thus obtainedcorresponds to that of the structure taken along a line A-A′ in FIG. 5A.

[0084] Next, as shown in FIG. 4C, an insulating film 330 is formed as abank. Although, in this embodiment, the bank 330 is formed by using anacrylic resin, it can also be formed by using a silicon oxide film.After the bank 330 has been formed, a surface treatment for the firsttransparent electrode 329 is conducted by applying ultraviolet lightthereto in an oxygen atmosphere. This treatment has an effect inIncreasing a work function of the first transparent electrode 329, and,furthermore, an effect of removing contaminants from the surfacethereof.

[0085] Organic EL films 331, 332 are then formed to a thickness of 50 nmrespectively. The organic EL film 331 is an organic EL film emittingblue light, and the organic EL film 332 an organic EL film emitting redlight. An organic EL film (not shown) emitting green light is alsoformed at the same time. In this embodiment, the organic EL films areformed separately for each pixel by using an evaporation method using ashadow mask. It is a matter of course that the separate formation of theorganic EL films can also be carried out by suitably choosing a printingmethod and an ink jet method.

[0086] In this embodiment, an example using each of the organic EL films331, 332 as a single layer is shown. A laminated structure using CuPc(copper phthalocyanine) as a hole injection layer is also effective. Inthis case, first, a copper phthalocyanine film is formed on the wholesurface, and an organic EL film emitting red light, an organic EL filmemitting green light, and an organic EL film emitting blue light arethen formed for respective pixels corresponding to red, green, and bluecolors.

[0087] When a green organic EL film is formed, Alq₃(tris-8-quinolinolatoaluminum complex) is used, and quinacridone orcoumarin 6 is added as a dopant. When a red organic EL film is formed,Alq₃ is used as a matrix material for the organic EL film, and DCJT,DCM1 or DCM2 is added as a dopant. When a blue organic EL film isformed, Balq₃ (5-configuration complex having a mixing ligand for2-methyl-8-quinolinol and a phenol derivative) is used, and perylene isadded as a dopant.

[0088] According to the present invention, the organic EL film is not,of course, required to limit to the above-mentioned organic EL film. Aknown low molecular weight organic EL film and a high polymer organic ELfilm can be used. When a high polymer organic EL film is used, a coatingmethod (spin coating method, an ink jet method, or a printing method)can also be used.

[0089] After the organic EL films 331, 332 are thus formed, a MgAg film(metallic film obtained by adding 1-10% silver (Ag) to magnesium (Mg))of 20 nm in thickness is formed as a second transparent electrode 333,and, furthermore, an ITO film of 250 nm in thickness as a thirdtransparent electrode 334. In this embodiment, the second and thirdtransparent electrodes 333, 334 constitute a cathode 341.

[0090] An EL element 400 made of the anode 340, organic EL film 331 (ororganic EL film 332), and cathode 341 is formed. In this embodiment,this EL element functions as a luminescent element.

[0091] Next, as shown in FIG. 4D, an auxiliary electrode 336 made of atransparent conductive film is formed to a thickness of 250 nm on theseal member 335, and an anisotropic conductor 337 made of an anisotropicconductive film on the third transparent electrode 334. The substrate301 and seal member 335 are pasted on each other by using a sealmaterial (not shown).

[0092] The pasting step is carried out in an argon atmosphere. As aresult, argon is sealed in a space 338. A gas used for sealing may, ofcourse, be any gas as long as it is an inert gas, and a nitrogen gas ora rare gas may be used. It is preferable that the space 338 be filledwith a material absorbing oxygen or water thereinto. It is also possibleto fill the space with a resin.

[0093] A switching TFT (p-channel type TFT in this embodiment) 401 and acurrent control TFT (p-channel type TFT in this embodiment) 402 areformed by the above-described manufacturing steps. Since all TFTs inthis embodiment are formed of p-channel type TFT, the manufacturingsteps are very simple.

[0094] The height-different portions are flattened by the secondinterlayer insulating film 324, and the drain wire 321 of the currentcontrol TFT 402 and the pixel 328 are electrically connected together byusing the anisotropic plug 327 buried in the contact hole 325, so thatthe flatness of the anode 340 is high. Accordingly, the uniformity ofthe thickness of the organic EL film 332 can be improved, and thisenables the emission of light from the pixels to become uniform.

Embodiment 2

[0095] In this embodiment, an EL luminescent apparatus having pixels thestructure of which is different from that of the pixels of the ELluminescent apparatus shown in FIG. 2 will be described with referenceto FIG. 7. The embodiment of FIG. 7 can be manufactured, by onlyslightly modifying the structure of FIG. 2, and will be described withattention paid to the points of the former embodiment which aredifferent from the corresponding points of the latter embodiment.Therefore, concerning the parts of the embodiment of FIG. 7 which aredesignated by reference numerals identical with those used in FIG. 2,the statement under “Description of the Preferred Embodiment” may bereferred to.

[0096] In the embodiment of FIG. 7, contact holes are formed in aninterlayer insulating film 205, and a pixel electrode 701 and a firsttransparent electrode 702 are thereafter formed in the same condition,an insulating film 703 being then formed so as to fill recessed portionsdue to contact holes therewith. In this embodiment, the insulating film703 is called a filling insulating film. Since the filling insulatingfilm 703 can be formed simultaneously with banks 209, it does not causethe number of the manufacturing steps to be increased in particular.

[0097] This filling insulating film 703 is formed for the purpose ofpreventing just as the anisotropic conductor plugs 206 of FIG. 2 theoccurrence of short-circuiting of the cathode and the anode ascribed tothe recessed portions made of the contact holes. During the formation ofthe filling insulating film 703, a height measured from an upper surfacethereof to that of the second transparent electrode 702 is preferablyset to 100-300 nm. When this height exceeds 300 nm, it causes theshort-circuiting of the cathode and anode to occur in some cases. Whenthis height becomes not larger than 100 nm, there is a possibility thatthe effect (effect in holding down the influence of electric fieldconcentration in edge portions of the pixel electrode) of the banks 209,which is formed simultaneously with the insulating film 703, lowers.

[0098] In this embodiment, a layer of an acrylic resin is formed to athickness of 500 nm by a spin coating method after the secondtransparent electrode 702 has been formed. The layer of acrylic resin isthen etched with an oxygen gas turned into plasma, until the thicknessof this layer (the portions of the layer in which the contact holes arenot provided) amounts to 200 nm. After the thickness of the film is thusreduced, the banks 209 and the filling insulating films 703 are formedby carrying out a patterning operation.

[0099] The construction of an upper surface of a pixel in thisembodiment is shown in FIG. 8. Referring to FIG. 8, a sectional viewtaken along a line A-A′ corresponds to FIG. 7. In FIG. 8, a seal member215 and an anisotropic conductor 217 are not shown. Since a basic pixelstructure is identical with that of FIG. 5, a detailed descriptionthereof is omitted.

[0100] As shown in FIG. 8, the bank 209 is formed so as to hide adifference in height between edge portions of the picture electrode 701and the anode 702, and the filling insulating film 703 is formed byprojecting parts of the bank 209. This projecting insulating film has astructure filling the recessed portions made of the contact holes of thepixel electrodes 701.

[0101] The EL luminescent apparatus in this embodiment can bemanufactured easily by combining the above method of forming the fillinginsulating film with the manufacturing method of Embodiment 1.

Embodiment 3

[0102] Although only the construction of pixels is shown in the ELluminescent apparatuses shown in the mode of embodiment and Embodiment1, a circuit for driving the pixels may be formed in a body on the samesubstrate. In this case, the driving circuit can be formed of an nMOScircuit, a pMOS circuit, or a CMOS circuit. It is, of course, allowableto form the pixel portions alone of TFTs, and use an externally fixeddriving circuit, typically, an IC tip-including driving circuit (TCP andCOG).

[0103] In Embodiment 1, the pixel portions are formed by p-channel typeTFTs only, and the number of the manufacturing steps are therebyreduced. In this case, it is also possible to form the driving circuitby a pMOS circuit, and use an IC tip-including driving circuit as adriving circuit unable to be formed by a pMOS.

[0104] The structure of this embodiment can be put into practice byfreely combining the same with the structure of Embodiment 1 or 2.

Embodiment 4

[0105] In this embodiment, an example using an amorphous silicon film asan active layer of switching TFTs and current control TFTs formed inpixel portions is shown. An inversely staggered TFT is known as a TFTusing an amorphous silicon film, and can also be used in thisembodiment.

[0106] Although a step of manufacturing a TFT using an amorphous film issimple, a size of an element becomes large. In the EL luminescentapparatus according to the present invention, the size of TFT does nothave influence upon the effective emission surface area. Therefore, amore inexpensive EL luminescent apparatus can be manufactured by usingan amorphous silicon film as an active layer.

[0107] The structure of this embodiment can be put into practice byfreely combining with any of those of Embodiments 1-3. However, when thestructure of Embodiment 4 is combined with that of Embodiment 3, it isdifficult to manufacture a driving circuit of a high operating speed bya TFT using an amorphous silicon film. Therefore, it is desirable toexternally fix an IC tip-including driving circuit to the structure.

Embodiment 5

[0108] In Embodiments 1-4, active matrix type EL luminescent apparatuseswere described. The present invention can also be put into practice withrespect to an EL element of a passive matrix type EL luminescentapparatus.

[0109] The structure of this embodiment can be put into practice byfreely combining the same with any of those of Embodiments 1-3. However,when the structure of Embodiment 5 is combined with that of Embodiment3, an IC tip-including driving circuit is necessarily fixed to an outerportion of the structure.

Embodiment 6

[0110] A luminescent apparatus formed by putting into practice thepresent invention can be used as a display of various kinds of electricappliances. The displays formed by inserting a luminescent apparatus ina casing include all information displays, such as a display forpersonal computers, a display for receiving a TV broadcast and a displayfor advertisement.

[0111] The electric appliances besides above to which the presentinvention can be applied include a video camera, a digital camera, agoggle type display (head mounting display), a navigation system, amusic reproducer (car audio and an audio component), a note typepersonal computer, a game machine, a portable information terminal(mobile computer, a portable telephone, a portable game machine, or anelectronic book), and an image reproducer (apparatus adapted toreproduce an image recorded on a recording medium, and an apparatusprovided with a display for showing the image).

[0112] As mentioned above, the range of application of the presentinvention is very wide, and the present invention can be used forelectric appliances in all fields. The electric appliances in thisembodiment may use a luminescent apparatus of any structures shown inEmbodiments 1-6.

[0113] The present invention is characterized in that an electrode madeof a transparent conductive film provided on a seal member iselectrically connected, by using an anisotropic conductive film, to anelectrode made of a transparent conductive film formed after an organicEL film is formed. This enables a resistance value of the transparentconductive film formed after the organic EL film is formed to besubstantially reduced, and a uniform voltage to be applied to atransparent electrode.

[0114] According to the present invention, a luminescent apparatushaving a greatly increased effective emission surface area of pixels andreproducing a bright high-quality image can be obtained by employing astructure which has a transparent or translucent cathode and areflecting electrode under an EL element, and which is adapted to takeout the light to the side of the cathode. An electric appliance usingthe luminescent apparatus according to the present invention as adisplay and reproducing an excellent image can also be obtained.

What is claimed is:
 1. A luminescent apparatus comprising: an electroluminescence element comprising an electrode having a reflectivesurface, a transparent electrode and an organic electro luminescencelayer interposed therebetween; an auxiliary electrode electricallyconnected to the transparent electrode via an anisotropic conductor. 2.A luminescent apparatus according to claim 1, wherein the reflectingsurface-including electrode is formed of a metallic film and thetransparent electrode is formed of a transparent conductive film.
 3. Aluminescent apparatus according to claim 1, wherein the reflectingsurface-including electrode is formed by laminating a metallic film anda transparent conductive film on each other and the transparentelectrode is formed by a laminating a translucent metallic film and atransparent conductive film on each other.
 4. A luminescent apparatusaccording to claim 3, wherein an organic electro luminescence layer isprovided in contact with the transparent conductive film included in thereflecting surface-including electrode and the translucent metallicfilm.
 5. A luminescent apparatus according to claim 3, wherein thetranslucent metallic film has a thickness of 5-70 nm.
 6. A luminescentapparatus according to claim 1, wherein the auxiliary electrode isformed of a transparent conductive film.
 7. A luminescent apparatusaccording to claim 1, wherein said a luminescent apparatus is anapparatus selected from the group consisting of a personal computer, aTV, a video camera, a digital camera, a goggle type display, anavigation system, a music reproducer and game machine.
 8. A method ofmanufacturing a luminescent apparatus, comprising the steps of: forminga reflecting surface-including electrode on an insulator, forming anorganic electro luminescence layer on the reflecting surface-includingelectrode, forming a transparent electrode on the organic electroluminescence layer, forming an anisotropic conductor on the transparentelectrode, forming an auxiliary electrode on a seal member, and pastingthe insulator and seal member on each other so that the anisotropicconductor and auxiliary electrode are connected together.
 9. A method ofmanufacturing a luminescent apparatus according to claim 8, wherein thereflecting, surface-including electrode is formed of a metallic film andthe transparent electrodes is formed of a transparent conductive film.10. A method of manufacturing a luminescent apparatus according to claim8, wherein the reflecting surface-including electrode is formed bylaminating a metallic film and a transparent conductive film on eachother and the transparent electrode is formed by laminating atranslucent metallic film and a transparent conductive film on eachother.
 11. A method of manufacturing a luminescent apparatus accordingto claim 10, wherein a thickness of the translucent metallic film is setto 5-70 nm.
 12. A method of manufacturing a luminescent apparatusaccording to any one of claim 8, wherein the auxiliary electrode isformed of a transparent conductive film.
 13. A luminescent apparatusaccording to claim 4, wherein the translucent metallic film has athickness of 5-70 nm.
 14. A luminescent apparatus comprising: asubstrate; a first electrode having a reflective surface over thesubstrate; an organic electro luminescence layer over the firstelectrode; a transparent electrode over the organic electro luminescencelayer; an anisotropic conductor over the transparent electrode; and anauxiliary electrode formed over the anisotropic conductor andelectrically connected to the transparent electrode via the anisotropicconductor.
 15. A luminescent apparatus comprising: a substrate; aswitching TFT formed over the substrate; a current control TFTelectrically connected to the switching TFT; a first electrode having areflective surface formed over the current control TFT; an organicelectro luminescence layer formed over the first electrode; atransparent electrode formed over the organic electro luminescencelayer; an anisotropic conductor formed over the transparent electrode;and an auxiliary electrode formed over the anisotropic conductor andelectrically connected to the transparent electrode via the anisotropicconductor.
 16. A luminescent apparatus comprising: an electroluminescence element comprising an electrode having a reflectivesurface, a first transparent electrode and an organic electroluminescence layer interposed therebetween; a second transparentelectrode electrically connected to the transparent electrode via ananisotropic conductor.
 17. A luminescent apparatus comprising: asubstrate; a first electrode having a reflective surface formed over thesubstrate; an organic electro luminescence layer formed over the firstelectrode; a transparent electrode formed over the organic electroluminescence layer; a plurality of conductive films disposed separatelyeach other, and formed on the transparent electrode; and an auxiliaryelectrode formed over the plurality of conductive layers, wherein theauxiliary electrode is electrically connected to the transparentelectrode via the plurality of conductive layers.
 18. A luminescentapparatus according to claim 1, wherein the anisotropic conductorcomprises a resin in which conductive particles are dispersed.
 19. Aluminescent apparatus according to claim 14, wherein the anisotropicconductor comprises a resin in which conductive particles are dispersed.20. A luminescent apparatus according to claim 15, wherein theanisotropic conductor comprises a resin in which conductive particlesare dispersed.
 21. A luminescent apparatus according to claim 16,wherein the anisotropic conductor comprises a resin in which conductiveparticles are dispersed.